﻿<p>A structural action is a structural activity that acts upon
a structural item or building element.</p>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC2x2.
</blockquote>

<blockquote class="change-ifc2x4">
IFC4 CHANGE&nbsp; Attribute <em>DestabilizingLoad</em> made optional.  Attribute <em>CausedBy</em> deleted; use <em>IfcRelAssignsToProduct</em> via <em>ReferencedBy</em> instead.
</blockquote>

<p class="use-head">Relationship use definition</p>
<p>Structural actions are grouped into either an <em>IfcStructuralLoadGroup</em> of predefined
type LOAD_GROUP or, more often, an <em>IfcStructuralLoadCase</em>.  This is accomplished via the
inverse relationship <em>HasAssignments</em> and an <em>IfcRelAssignsToGroup</em> relationship object.
<em>IfcStructuralLoadGroup.LoadGroupFor</em> or <em>IfcStructuralLoadCase.LoadGroupFor</em> respectively
refers to the structural analysis model(s) in which the loads are used.</p>

<p>It is furthermore possible to establish relationships between actions in one analysis model
and reactions in another analysis model which cause the actions.  For example, a support reaction
from one structural system may be taken over as a load onto another supporting structural system.
This is expressed by means of the inverse relationship <em>ReferencedBy</em> of the action and an
<em>IfcRelAssignsToProduct</em> relationship object.  <em>IfcRelAssignsToProduct.Name</em> is set to
'Causes' and <em>IfcRelAssignsToProduct.RelatedObjects</em> refers to an instance of a subtype of
<em>IfcStructuralReaction</em>.</p>